Heat and mass transfer analysis of natural convection in a liquid desiccant closed-loop system: The effect of heat source and heat sink temperature

Abstract

Considering the importance of providing healthy and suitable indoor air condition efficiently, liquid desiccant air condition systems are the focus of study in recent years. The concept of natural convection heat and mass transfer loop is introduced. The system is a closed-loop consisting of two three-fluid hollow fiber membrane heat and mass transfer exchangers played as absorber and regenerator. The system was run under standard conditions with an inlet air flow rate of 6 m3/h. The sensitivity analysis was made to reveal the effect of heat source and heat sink temperature on the system performance. The heat sink and heat source temperature lie between 15–25 °C and 50–70 °C respectively and the outlet air temperature and humidity ratio, moisture removal rate, cooling capacity and coefficient of performance are the evaluating indexes. The results show that despite the convectional desiccant loops the high solution flow rate is not desirable and instead the concentration gradient in the loop is the most important factor. For each heat source temperature, there is an interval of heat sink temperature for which the solution flow rate is the maximum and the concentration gradient is the minimum. Under operating conditions of the present study, the maximum obtained COP is 0.71 which is for temperature pair of (55 °C, 20 °C).

Keywords

• Moisture removal rate
• Lithium chloride solution
• Cooling capacity
• Sensible heat factor
• Desiccant flow rate